Concept of dimensionality
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Concept of Dimensionality. Concept of Dimensionality (Cont.). PROCESSING GAIN = P G. Processing gain is the improvement seen by a spread spectrum system in SNR, within the system’s information bandwidth, over the SNR in the transmission channel. P G = B S / B i = R S / R i.

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Concept of Dimensionality

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Concept of dimensionality

Concept of Dimensionality


Concept of dimensionality cont

Concept of Dimensionality (Cont.)


Concept of dimensionality

PROCESSING GAIN = PG

Processing gain is the improvement seen by a spread spectrum system in SNR, within the system’s information bandwidth, over the SNR in the transmission channel.

PG = BS / Bi = RS / Ri

Typical PG = 20 to 60 dB


Concept of dimensionality

JAMMING MARGIN = MG

Jamming margin takes into account the requirement for a useful system output SNR and allow for internal losses.

MG = GP – [Lsys + (S/N)out ] , dB

Where,

Lsys = system implementation losses

(S/N)out = SNR at information, despread, output


Digital modulation techniques

DIGITAL MODULATION TECHNIQUES

  • Information signals (baseband signals) must be processed before transmission to be compatible with the channel

  • A baseband signal modulates a high frequency carrier by varying the carrier’s phase, amplitude, or frequency

  • In digital systems there are 3 basic modulation schemes:

    • Phase shift keying (PSK)

    • Amplitude shift keying (ASK)

    • Frequency shift keying (FSK)

  • In general modulated signal is of the form:

    S(t) = A(t) cos [2pfo t + f(t)]


Binary phase shift keying bpsk

Binary Phase Shift Keying (BPSK)


Bpsk circuit implementation

BPSK Circuit Implementation


Binary amplitude shift keying bask

Binary Amplitude-Shift Keying (BASK)


Spectrum of bask

Spectrum of BASK

  • ASK differs from PSK in that ASK has carrier component due to DC value of m(t)


Binary frequency shift keying bfsk

Binary Frequency-Shift Keying (BFSK)


Bfsk power spectrum

BFSK Power Spectrum


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